Our government called the terror attacks on our country an act of war and replied with a declaration of war on terrorism. What can history teach us about our prospects in such a war?

The lessons of history do not suggest that the United States can’t wage wars in coalition. But the coalitions that have worked best have been uneasy assemblages of states bound together by genuine and vital (if transient) common interests. Washington has been speaking about persuading our new allies to understand that ending state support for terrorism is in everyone’s interest. But this is plainly false: A number of our theoretical allies are states that have a strong vested interest in employing terrorists, because terrorists have proved a cheap, effective, and apparently satisfying way of striking at enemies. If we intend to fight the war on terror the way we fought the Gulf War, by appealing to some least common denominator of political agreement, we may be in trouble from the start. And we may be in trouble simply by terming a prospective military action a war on terror.

To declare war on terrorism, to call acts of terrorism acts of war, also runs the risk of fighting a previous campaign. War, if it is anything more than a metaphor, is waged by and between states, and when we forget this we are liable to get into difficulties. A few years ago we declared war on drugs, but the results of that war are pretty discouraging, not least because we thereby framed the question in a way that suggests the satisfying outcome of a violent and total result, but also because the tools of war we possess in abundance have not proved very useful. States may harbor drug traffickers, but we have not thought it useful to invade Mexico, Colombia, Burma, or Thailand. Aircraft may fly drugs into the United States, but we do not send F-16s to shoot them down; ships may land drugs on our coasts, but we use Coast Guard cutters to intercept them, not destroyers to sink them. War is something we are good at; suppressing the drug trade is something we are less good at. The price we pay for calling a narcotics problem a war is to cast undeserved doubt on our military capacity.

Is rhetoric about a war on terrorism the same sort of mistake? Maybe, but not necessarily. Terrorism is often used by states that don’t have the means or the stomach to wage a fullscale war and thus wage a stifled one with surrogates. Syria has used terrorists against both Israel and Turkey, Pakistan used them against India, Iraq and Iran against each other and the United States, Libya against a variety of enemies. The Soviet Union backed some terrorists while shunning others (for example, the IRA). The Chinese and Cubans both backed some terrorist organizations. Our own government has supported guerrillas who on occasion used terrorist methods; to pick a relatively uncontroversial example, we backed Afghan mujahedeen who were less than scrupulous in their tactics. This list is very far from exhaustive.

One can certainly make war on states, and there may be advantages to doing so when attempting to suppress terrorism. Most successful terrorists make good use of the resources states can provide; when those resources aren’t available, suppressing terror generally gets easier. States are also clear targets, while terrorists themselves are usually very hard to find. And while terrorists may scorn the risks they run, may even seek martyrdom, states almost never seek martyrdom. States can be deterred by reprisal, or destroyed.

This is indeed what some members of the administration have vowed to do: We are going to “end” states that support or give shelter to terrorists. War is a way of ending states, but ending a state requires military conquest, occupation, and probably the organization of a successor government. It is perfectly possible to do this. Three states that not only supported terrorism but actively practiced it declared war on the United States in 1941. Germany, Japan, and Italy no longer practice terror or support it. But 50 years later, in 1991, when the United States had a good chance to solve a problem of statesupported (and indeed state-conducted) terrorism, it left a terrorist regime in control of Iraq.

Why did the rules ever evolve in a direction that allowed states to shelter terrorists, and use them fairly freely? Some terrorists have been employed by states so strong that we did not think it prudent to go to war with them. Invading East Germany to root out members of the Baader-Meinhof gang would have meant pushing through Soviet Guard tank armies. Guerrillas, who have a tendency to use terrorist methods, and who by the older rules of war were themselves terrorists, were employed by both sides during the Cold War; they often seemed to be the only prudent way of striking at the enemy. And guerrillas often did their work in the reflected glory of the partisans and Resistance fighters of the Second World War. So state support of terror was tolerated, sometimes because it had to be and sometimes because such support seemed morally acceptable, or even morally commendable, in a context of the Cold War and anti-imperialist wars.

The end of the European empires and the disappearance of the Soviet Union did not immediately undo this atmosphere of toleration, and, in any case, the effect of the Cold War on the toleration of state-supported terror was sometimes indirect. Revolutionary Iran was not a Soviet client, but it did employ terror against the United States, and did so with no fear of invasion or of massive bombardment. Perhaps this forbearance, too, was a result of Cold War politics; precisely because revolutionary Iran was not in the Soviet orbit, American administrations were wary of pushing her there.